1. Field of the Invention
This invention relates to a recording apparatus for performing recording with an ink jet recording head.
2. Related Background Art
There are various recording apparatuses, which perform recording on recording media such as paper and OHP sheet (hereinafter referred to as recording paper or merely paper). These recording apparatuses use a recording head mounted on them. The recording head used is of various systems such as wire dot system, heat-sensitive system, heat transfer system and ink jet system.
Among these recording systems, the ink jet system is one, in which ink is ejected directly toward recording paper. Therefore, its running cost is inexpensive, and it is noted as a quiet recording system.
The recording system based on the ink jet system generally uses a recording head having an array of fine ink discharging orifices. Therefore, when it is desired to operate the recording head for long time, capping is done in order to prevent intrusion of air bubbles and dust inwards from discharging orifices or to prevent ink from becoming defectively ejectable and unsuited for recording due to increase of its viscosity resulting from evaporation of its solvent. The capping is done as follows. A cap is provided, which can cover an orifice-formed face of recording head. The orifice-formed face is covered by the cap when the recording head is not used.
However, in case when a state of defective ejection as noted above is produced in spite of the capping or when discharging orifices not or less used according to a print pattern become defectively electable during recording operation, it is effective to flush the ink for removing the cause of such defective ejection (the process being referred to as ejection recovering process).
In one form of a means for carrying out such ejection recovering process, ink ejection energy generators provided inside the discharting orifices of the recording head are driven to cause ejection of ink from all the discharging orifices toward the cap used for the capping noted above (the ejection being hereinafter referred to as preliminary ejection). This is done for the purpose of removing the cause of defective ejection together with ink. An ink absorbing member is provided inside the cap opposing the discharging orifices for preventing leakage or spattering of ink coming out from the discharging orifices at the time of preliminary ejection.
Further, a pump is provided in communication with and to provide an absorbing force to the cap. The pump serves to absorb ink remaining in the cap after preliminary ejection toward it (the absorption being hereinafter referred to as dry absorption), thus preventing deterioration of ink absorption capacity or reduction of ink absorbing force due to solidification of ink within the absorbing member.
To carry out the dry absorption as noted above, a time for restoring the recording head to the capping position and also a time for operating the pump are necessary, and the timing for effecting dry absorption is important for improving the speed of recording.
In the prior art ink jet recording apparatus, the time for restoring the recording head is reduced by carrying out the dry absorption in an interlocked relation to the capping. The capping is effected in case when the recording head is not operated for long time, for instance in such case as when recording is interrupted for no recording data is transferred for a predetermined period of time during recording operation or when recording is interrupted after the end of recording of one page. This means that dry absorption is carried out before capping.
Since in the prior art ink jet recording apparatus the dry absorption is carried out in an interlocked relation to the capping, there are cases when the dry absorption is unnecessarily executed many times. For example, it is executed even in the absence of recording data transferred for a predetermined period of time during recording.
The ink receiving capacity of the cap varies depending on the volume thereof or on the ink absorbing member, but it is such that ink elected in plurality of times of preliminary ejection can be received. Therefore, carrying out preliminary ejection in spite of sufficiently redundant ink receiving capacity leads to increasing the number of times of dry absorption and also the recording period.
Since the preliminary ejection requires time for restoring the recording head to the capping position and also time for driving the head as noted above, for reducing the recording time it is necessary to reduce the number of times of preliminary ejection. In the prior art recording apparatus, preliminary ejection is carried out periodically lest defective ejection of ink from the head should result during recording as well. More specifically, time elapsed after the previous preliminary ejection is measured, and preliminary ejection is caused whenever a predetermined period of time is passed.
In practice, when recording operation is interrupted and capping is executed, and timer is cleared, the cap is opened, and time measurement is effected once again when resuming the recording operation. This means that when the recording head is held capped for long time or when capping operation is caused frequently in the predetermined period of time noted above, preliminary ejection is not effected before defective ejection results.
Further, where preliminary ejection is done whenever the cap is opened, the number of times of preliminary ejection is increased, although defective ejection will not result.
As shown, with the prior art ink jet recording apparatus the timing of preliminary ejection is determined without considering the period of capping. Therefore, there are problems of occurrence of defective ejection of the recording head and increase of number of times of preliminary ejection.